Many analytical instruments use the intensity of light of various colors over a range of wavelengths to study the composition of matter, both qualitative and quantitative. When light interacts with matter, it may undergo many processes including but not limited to absorption, scattering, reflection, refraction, fluorescence, and phosphorescence. Instruments are now available to measure the extent of these processes with good precision and accuracy throughout the ultraviolet, visible, near-infrared, infrared, and other regions of the electromagnetic spectrum. It is generally true that the closer a measurement is made to the information source most related to solving a problem, the less chance there is that delay, added noise, or contamination will confound accurate characterization of the system under study. Instruments that can provide a direct and immediate benefit to the general public, however, such as those for measuring water quality, the presence of contamination in food, presence of common infectious bacteria, soil composition, or the identity of questionable substances remain uncommon and used only by those with specialized training—due, in part, to cost and ease of use.